The present invention relates to an apparatus for detecting a target position and method therefor utilizing a radar device.
A first previously proposed target position detecting apparatus will be described below.
A light emitting diode (LED) is provided which emits visible light pulses or ultra-red light pulses, receiving a command from a signal processor. Generally, since a width (or solid angle or divergence angle) of the light beams from the LED is very large (or very wide), a throttling of the light beams using a lens group is used to narrow the light beams. Then, the throttled light beams are reflected by means of a rotary mirror to direct toward a target. It is noted that an angle of the rotary mirror with respect to the target is adjusted by means of the signal processor and the rotation of the rotary mirror causes the light beams to scan an area surrounding the target.
When the light beams are reflected on the beam impinged target, the reflected light beams are passed through a lens and reached to a light receiving element (device). The signal processor measures a time difference between the time at which the light beams are emitted from the light emitting diode to the time at which the light beams are received by the light receiving element. According to a rotation angle of the rotary mirror, a direction of the target is accordingly calculated. A laser may be used in placed of the LED.
Next, a second previously proposed target position detecting apparatus will be described below.
Ultrasonic waves generated by means of a speaker are reflected by means of the target and reached to a microphone. The signal processor measures a time duration from a time at which the ultrasonic waves are irradiated from the speaker to a time at which the reflected ultrasonic waves are reached to the target so as to enable the calculation of a distance from the apparatus to the target. In the latter case, the ultrasonic wave beams are throttled and the speaker is rotated by means of such a drive source as a motor to enable scanning over the target. The direction of the target can be calculated according to the scanning of the ultrasonic waves over the target.
A co-pending U.S. patent application Ser. No. 08/289,087 filed on Aug. 11, 1994 (which corresponds to a German Patent Application No. P 44 026.8 (filed on Aug. 24, 1994 and published as DE 44 30 026 A1 on Mar. 9, 1995) and corresponds to a French Patent Application No. 94 10 495 (filed on Aug. 31 1994 and published as No. 27 09 558 (No. 10 issued on Mar. 10, 1995)) exemplifies a third previously proposed target position detecting apparatus using the radar device.
However, each of the previously proposed target position detecting apparatuses requires the throttled light beams and a rotation mechanism for the throttled (converged) light beams to be scanned over the area surrounding the target. Consequently, a cost of manufacturing each of the previously proposed the target position detecting apparatuses becomes relatively high and a reliability of the apparatus due to such a mechanical loss as a wear-out of the rotation mechanism (in an engaged mechanism between the rotation mechanism and the drive source) becomes reduced. Furthermore, since a rotation speed of the rotation mechanism is so slow that the scanning speed is correspondingly very slow and that a detection time until the target is located by the scanning operation tends to become accordingly longer.
Furthermore, in each of the previously proposed target position detecting apparatuses, the direction of the target is detected from a (mechanical) rotating mechanism. Therefore, each of the previously proposed apparatuses requires the highly accurate rotating mechanism and requires a precisely controlled detection mechnism of a rotating angle of the rotating mechanism. Consequently, it becomes difficult to reduce costs of manufacturing the target position detecting apparatuses.